1. Field of the Invention
The present invention relates to a structure for arranging large-capacity electrical double-layer capacitor cells within narrow confines of space.
2. Description of the Related Art
An electrical double-layer capacitor has a large capacity as compared with other types of capacitor and has hitherto been used as a power source for backup, or the like.
FIG. 6 illustrates a conventional electrical double-layer capacitor cell (hereinafter simply referred to as the cell in some cases). As shown, a cell C comprises the following components: a collecting electrode 1; a sealing material 2; two electrode layers 3; and a porous separator 4.
The sealing material 2 has a cylindrical configuration, and the porous separator 4 is disposed in a substantially central portion of its interior. The electrode layer 3 is filled on each opposite side of the porous separator 4, and the collecting electrode 1 is placed in such a manner as to cover the surface of the electrode layer 3 and the rim of the sealing material 2.
As the collecting electrode 1, an electrically conductive rubber sheet, for example, may be used, and as the sealing material 2, non electrically conductive rubber, for example, may be used. As the porous separator 4, a polypropylene porous film, for example, may be used. In addition, as the electrode layer 3, paste made by mixing activated carbon particles and dilute sulfuric acid may be used.
FIG. 7 illustrates a conventional electrical double-layer capacitor formed by combining a plurality of cells C having the above described arrangement. As shown, the electrical double-layer capacitor comprises the following components: a case 5; electrode plates 6, 7; terminals 6-1, 7-1; an insulating plate 8; reinforcing plates 9, 10; and the cells C.
The reinforcing plate 9 is connected to the electrode plate 6, while the reinforcing plate 10 is connected to the electrode plate 7 via the case 5. The terminal 6.1 is formed by cutting out a part of the electrode plate 6, while the terminal 7-1 is formed by cutting out a part of the electrode plate 7. The insulating plate 8 is inserted between the electrode plates 6 and 7 to provide insulation therebetween.
If the cells C are simply laminated, the contact resistance of activated carbon particles of the cells C is large, so that the internal resistance of the capacitor is large. Hence, it is common practice to calk the rim of the case 5 at the time of lamination so as to apply pressure to the laminated body, which reduces the aforementioned contact resistance, thereby rendering the internal resistance of the capacitor small.
In the above-described example, pressurization is conducted not at the stage of individual cells but after the lamination thereof. However, in some cases, pressurization processing is effected at the stage of individual cells.
FIG. 8 illustrates a cell of an electrical double-layer capacitor of a button type. As shown, this cell comprises the following components: collecting electrodes 11, 12; two electrode layers 13; a porous separator 14; a sealing material 15; and an insulating material 16.
The collecting electrode 12 is formed into a cylindrical configuration and accommodates therein the electrode layer 13, the porous separator 14, the sealing material 15, etc. This assembly is pressed with the collecting electrode 11 from thereabove, and the rim of the collecting electrode 12 is calked inwardly, thereby fabricating a cell. The calking force of the collecting electrode 12 provides the pressurizing force, thereby rendering the internal resistance small.
FIG. 9 shows an electrical double-layer capacitor in which button-type cells are laminated. In order to obtain a desired voltage, a necessary number of cells are laminated and are accommodated in an outer case 17. In this case, it suffices if electrical contact is secured, and there is no need to provide pressurization.
As described above, in conventional electrical double-layer capacitors, the cells C are disposed by being laminated.
It should be noted that, as a prior-art document concerning electrical double-layer capacitors, for example, Japanese Patent Laid-Open No. 2621/1981 is known.
However, there has been a problem in that if a request is made to install a large-capacity electrical double-layer capacitor within narrow confines of space, it is impossible to meet the request with the conventional way of laminating cells.
For instance, when it is desirous to install an electrical double-layer capacitor within narrow confines of space such as between a pair of inner and outer panels constituting a wall of an automobile, the conventional structure of lamination would result in an increased thickness for the capacitor, thereby making the installing impossible.